feat: propagate custom genai generate_content attributes to logs, in addition to spans (#4103)

* feat propagate custom genai generate_content attributes to logs in addition to spans

* Put the extra attributes on logs that follow the old semanting convention as well

* Use dict[str, AttributeValue] instead of dict[str, Any]

* Revert "Put the extra attributes on logs that follow the old semanting convention as well"

This reverts commit 72a5c99cadacd5113d648918910a291df9c86cb6.

* Update CHANGELOG.md

* Fix lint

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Co-authored-by: Aaron Abbott <aaronabbott@google.com>